JP3444995B2 - Electrophotographic photoreceptor and electrophotographic apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member and an electrophotographic apparatus, and more particularly to an electrophotographic photosensitive member having a non-contact charge of a DC voltage, and an electrophotographic apparatus including the photosensitive member.

[0002]

2. Description of the Related Art In an electrophotographic method, for example, selenium,
When an image is obtained by performing basic processes such as charging, exposure, development, transfer, fixing, and cleaning on an electrophotographic photoreceptor such as cadmium sulfide, zinc oxide, amorphous silicon, and organic photoconductor, the charging process is Almost all metal wires are charged by a corona generated by applying a high voltage (DC 5 to 8 kV). However, with this method, corona products such as ozone and NO _x deteriorate the surface of the photoconductor when corona occurs, causing image blurring and deterioration, and wire stains affect image quality, resulting in image white spots and black streaks. There was a problem such as causing. In particular, electrophotographic photoconductors whose photosensitive layer is composed mainly of organic photoconductors have lower chemical stability than other selenium photoconductors and amorphous silicon photoconductors, and chemically react when exposed to corona products. (Mainly oxidation reaction) occurs and tends to deteriorate. Therefore, when it is repeatedly used under corona charging, image blurring due to the above-mentioned deterioration and low copy density due to a reduction in sensitivity occur, and the printing (copying) resistance tends to be shortened.

In the case of corona charging, the electric current directed to the photosensitive member is only 5 to 30% in terms of electric power, and most of the electric current flows to the shield plate, which is inefficient as a charging means.

In order to make up for such a problem, JP-A-57-178267 and JP-A-57-178267 do not use a corona discharger.
-104351, 58-40566, 58-1
A method of contact charging has been studied, as proposed in Japanese Patent Nos. 39156 and 58-150975.

Specifically, the surface of the photoconductor is charged to a predetermined potential by contacting the surface of the photoconductor with a charging member such as a conductive elastic roller to which a direct current voltage of about 1 to 2 kV is applied from the outside. Is.

Further, there is also one in which the surface of the photoconductor is charged by a charging member to which a direct current voltage of about 1 to 4 kV is applied in a non-contact manner with the photoconductor.

However, in spite of many proposals for the direct charging method regardless of whether it is contact or non-contact, there is almost no market record. The reasons for this are the non-uniform charging and the occurrence of discharge dielectric breakdown of the photoconductor due to direct application of voltage. Due to the non-uniformity of charging, the length of the surface to be charged is 2 to 20
In the case of the so-called white stripe (a phenomenon in which white stripes appear in a solid black or halftone image) which occurs in the case of the positive development method, or the case of the reversal development method, which causes stripe-shaped charging unevenness of about 0 mm and a width of 0.5 mm or less. This will lead to image defects such as black streaks.

In order to solve such problems and improve the uniformity of charging, a method has been proposed in which an AC voltage is superimposed on a DC voltage and applied to a charging member (Japanese Patent Laid-Open No. 63-63).
(See Japanese Patent Publication No. 149668). In this charging method, a pulsating voltage is applied by superimposing an _AC voltage (VAC) on a DC voltage ( _VDC ) to perform uniform charging.

In this case, while maintaining the uniformity of charging, white spots in the positive development system, black spots in the reversal development system,
In order to prevent image defects such as fogging, it is necessary that the superimposed AC voltage has a peak-to-peak potential difference (V _PP ) that is at least twice the DC voltage.

However, if the superposed AC voltage is increased in order to prevent image defects, the maximum applied voltage of the pulsating voltage causes discharge dielectric breakdown at a slight defective portion inside the photosensitive member. In particular, when the photoconductor is an OPC photoconductor having a low withstand voltage, this dielectric breakdown is remarkable. In this case, in the normal development method, the image is white in the longitudinal direction of the contact portion, and in the reversal development method, black opacity occurs. Further, when there is a pinhole, there is a problem in that the portion becomes a conduction path, current leaks, and the voltage applied to the charging member drops.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned problems and to provide a streak having a length of 2 to 200 mm and a width of 0.5 mm or less due to non-uniformity of DC proximity non-contact charging. An electrophotographic photosensitive member that does not generate (a direction perpendicular to the moving direction of the surface to be charged), has a long copying life of the photosensitive member, and can stably supply a high-quality copy image, and An object is to provide an electrophotographic apparatus including a photoconductor.

[0012]

As a result of repeated studies on the above-mentioned problems, the inventors of the present invention have found that when a non-contact charge is applied to a photoconductor from a charging member by applying only a DC voltage, It has been found that the problem can be solved by improving the photoreceptor.

The above object is achieved by the present invention described below. That is, the present invention has a non-contact closely spaced charging member in an electrophotographic photosensitive member and the electrophotographic photosensitive member, said
The volume resistance value of the charging member is in the range of 10 ⁰ to 10 ¹² Ω · cm.
In the electrophotographic photosensitive member for an electrophotographic apparatus, which charges the surface of the electrophotographic photosensitive member by applying only a DC voltage to the electrophotographic photosensitive member, 1 cm ^{2 of the} electrophotographic photosensitive member Capacitance C per hit is 95 pF or more 140
Disclosed is an electrophotographic photosensitive member characterized by pF or less , and an electrophotographic apparatus equipped with the electrophotographic photosensitive member, preferably a distance (gap) between the electrophotographic photosensitive member and the charging member. l satisfies the following relational expression (I). 30μm ≦ l ≦ 90μm (I)

The present invention will be described in detail below. The non-contact charging method in which the charging member is brought into contact with the electrophotographic photosensitive member in a non-contact manner to perform charging is performed in a minute space between the photosensitive member and the charging member by void breaking discharge according to Paschen's law. Generally, in an electrophotographic apparatus, a photosensitive member having a drum shape or a belt shape is used, and both are charged while being rotated or moved with respect to a charging member. At this time,
Although void-breaking discharge is performed according to Paschen's law, due to the nature of such charging mechanism, there are many factors such as relative permittivity of the photoconductor, film thickness (electrostatic capacity), electrostatic capacity of charging member, resistance value, applied voltage, etc. It is not easy to uniformly charge due to factors. As one example of measures against this, a method of applying a pulsating current voltage on which an AC voltage is superimposed has been proposed.

In the present invention, when the charging is applied by the pulsating voltage, the electrostatic capacitance C per 1 cm ^{2 of} the photoconductor is set to 95 pF or more and 140 pF or less even when only the DC voltage is applied. It can be uniformly charged in the same manner as.

That is, the electrostatic capacity C per 1 cm ^{2 of} the photoconductor is
By setting it to 95 pF or more and 140 pF or less , it is possible to stably suppress the generation of an electric field in the opposite direction, which is considered to be the cause of streak images, etc., and the charging characteristics as a whole are the same as when applied by pulsating voltage. In addition, it is considered that uniform charging was possible without streak images. Furthermore,
Since the AC voltage is not superimposed, the above-mentioned harmful effects do not occur. Also, set the resistance value of the charging member to 5 × 10 ⁵
It is more effective if the resistance is increased to a value of Ω · cm or more.

FIG. 1 shows the basic construction of the electrophotographic apparatus of the present invention. The charging member 1 is arranged in non-contact proximity to the electrophotographic photosensitive member 2, and charges the photosensitive member 2 with a voltage applied from the connected external power source 3. The distance between the electrophotographic photosensitive member and the charging member is 30 to 300 μm, preferably 30 to 90 μm. 2a is a photosensitive layer and 2b is a conductive support.

[0018] The shape of the charging member 1 used in the present invention, other plates of curvature as shown in FIG. 1, the plate may be of any blade shape or the like shape, specification of an electrophotographic apparatus And can be selected according to the form. In addition, as the material of the charging member, a conductive metal material such as a metal such as aluminum, iron, or copper, a conductive polymer material such as polyacetylene, polypyrrole, or polythiophene, carbon, titanium oxide, a metal, or the like is electrically treated to have an insulating property. Resin, rubber or artificial fiber,
Alternatively, an insulating material such as polycarbonate, polyvinyl, or polyester whose surface is coated with a metal or another conductive material can be used. The volume resistance value of the charging member is in the range of 10 ⁰ to 10 ¹² Ω · cm, particularly 10 ⁵ to 1
The range of 0 ¹⁰ Ω · cm is preferable.

Examples of the organic photoconductor include those using an organic photoconductive polymer such as polyvinylcarbazole, and those containing a low molecular weight organic photoconductive substance in a binder resin.

In the electrophotographic photosensitive member shown in FIG. 2, a photosensitive layer 11 is provided on a conductive support 10 and the photosensitive layer 1 is provided.
1 has a laminated structure of a charge generation layer 13 in which a charge generation material (not shown) is dispersed and contained in a binder resin, and a charge transport layer 14 in which a charge transport material (not shown) is contained.
In this case, the charge transport layer 14 is laminated on the charge generation layer 13.

In the electrophotographic photoreceptor shown in FIG. 3, unlike the case of FIG. 2, the charge transport layer 14 is laminated below the charge generation layer 13. In this case, the charge generation layer 13 may contain a charge transport substance.

In the electrophotographic photosensitive member shown in FIG. 4, a photosensitive layer 11 is provided on a conductive support 10, and the photosensitive layer 1 is provided.
In No. 1, a binder resin contains a charge generating substance 12 and a charge transporting substance (not shown). Further, an overcoat layer can be applied in addition to the structure shown in FIGS.

As the conductive support 10, a metal such as aluminum or stainless steel, a cylindrical cylinder such as paper or plastic, a sheet or a film is used. Further, these cylindrical cylinders, sheets or films may have a conductive polymer layer or a resin layer containing conductive particles such as tin oxide, titanium oxide and silver particles, if necessary.

An undercoat layer (adhesive layer) having a barrier function and an undercoat function can be provided between the conductive support and the photosensitive layer. The subbing layer is for improving adhesion of the photosensitive layer, improving coatability, protecting the support, covering defects on the support, improving charge injection from the support, protecting the photosensitive layer against electrical breakdown, etc. It is formed. The film thickness is about 0.2 to 2 μm.

As the charge generating substance, pyrylium, thiopyrylium dye, phthalocyanine pigment, anthanthrone pigment, dibenzpyrenequinone pigment, pyratron pigment, azo pigment, indigo pigment, quinacridone pigment, asymmetric quinocyanine, quinocyanine, etc. should be used. You can

As the charge transport material, hydrazone compounds, pyrazoline compounds, styryl compounds, oxazole compounds, thiazole compounds, triarylmethane compounds, polyarylalkane compounds, etc. can be used.

The charge generating layer 13 includes a homogenizer, an ultrasonic wave, a ball mill, a vibrating ball mill, a sand mill, an attritor, a roll mill and the like together with the binder resin in an amount of 0.3 to 4 times the amount of the charge generating substance and the solvent. It is formed by being well dispersed, coated and dried according to the method used. The thickness is preferably 5 μm or less, and particularly preferably 0.01 to 1 μm.

The charge transport layer 14 is generally formed by dissolving the above charge transport material and the binder resin in a solvent and applying the solution. The mixing ratio of the charge transport material and the binder resin is 2: 1 to
It is about 1: 2. As the solvent, ketones such as acetone and methyl ethyl ketone, esters such as methyl acetate and ethyl acetate, aromatic hydrocarbons such as toluene and xylene,
Chlorinated hydrocarbons such as chlorobenzene, chloroform and carbon tetrachloride are used. When applying this solution, a coating method such as a dip coating method, a spray coating method and a spinner coating method can be used, and drying is performed at a temperature in the range of 10 to 200 ° C, preferably 20 to 150 ° C. At 5 minutes to 5 hours, preferably 10 minutes to 2 hours under blast drying or static drying.

As the binder resin used to form the charge transport layer 14, acrylic resin, styrene resin,
A resin selected from polyester, polycarbonate resin, polyarylate, polysulfone, polyphenylene oxide, epoxy resin, polyurethane resin, alkyd resin, unsaturated resin and the like is preferable. Particularly preferred resins include polymethylmethacrylate, polystyrene, styrene-acrylonitrile copolymer, polycarbonate resin or diallyl phthalate resin.

Further, the charge generation layer or charge transport layer comprises
Various additives such as an antioxidant, an ultraviolet absorber and a lubricant can be contained. Further, a protective layer may be further coated on the photosensitive layer.

A specific example of an electrophotographic apparatus using the electrophotographic photosensitive member of the present invention is shown in FIG. In this apparatus, a curved plate-shaped charging member 1, an image exposure unit 4, a developing unit 5, a transfer charger 6, a cleaner 7, and a pre-exposure unit 8 are arranged on the peripheral surface of the electrophotographic photosensitive member 2. G ₁ is a discharge part.

In the image forming method, first, a voltage is applied to the charging member 1 which is arranged in the non-contact proximity on the electrophotographic photosensitive member 2, the surface of the photosensitive member 2 is charged, and the original is exposed by the image exposing means 4. A corresponding image is exposed on the photoconductor 2 to form an electrostatic latent image. Next, the toner in the developing device 5 is attached to the photoconductor 2 to develop (visualize) the electrostatic latent image on the photoconductor 2. Further, the toner image formed on the photoconductor 2 is transferred onto the supplied transfer material P such as paper by the transfer charger 6, and is left on the photoconductor 2 without being transferred onto the transfer material by the cleaner 7. Collect toner.

If residual charges remain inside the photoconductor, it is better to irradiate the photoconductor 2 with light by the pre-exposure means 8 to eliminate the charge. On the other hand, the transfer material on which the toner image is formed is sent to a fixing device 9 by a conveying unit (not shown) and the toner image is fixed.

In this image forming apparatus, the image exposure means 4
As the light source of, a halogen light, a fluorescent lamp, a laser light or the like can be used. Also, other auxiliary processes may be added if necessary. FIG. 6 is a block diagram showing an example of using the electrophotographic apparatus of the present invention as a printer for a facsimile.

The controller 111 controls the image reading section 110 and the printer 119. The entire controller 111 is controlled by the CPU 117. Image reading unit 1
The read data from 10 is transmitted to the partner station via the transmission circuit 113. The data received from the other station is the receiving circuit 1
12 to the printer 119. The image memory 116 stores predetermined image data. The printer controller 118 controls the printer 119.
114 is a telephone.

The image information received from the line 115 (image information from a remote terminal connected through the line) is
After being demodulated by the receiving circuit 112, a decoding process is performed by the CPU 117 and sequentially stored in the image memory 116. When the image information of at least one page is stored in the memory 116, the image recording of that page is performed. CPU1
Reference numeral 17 reads out one page of image information from the memory 116 and sends the decoded one page of image information to the printer controller 118. Printer controller 118
Upon receiving the image information of one page from the CPU 117, the printer 119 controls the printer 119 to record the image information of the page.

The CPU 117 receives the next page during recording by the printer 119. The image is received and recorded as described above.

The electrophotographic photosensitive member of the present invention can be used in an electrophotographic copying machine, but is also widely used in electrophotographic application fields such as laser beam printers, CRT printers, LED printers, liquid crystal printers and laser plate making. Can be used.

[0039]

EXAMPLES The present invention will be specifically described below based on examples, but the present invention is not limited thereto.

Example 1 An aluminum cylinder having a diameter of 80 mm and a length of 360 mm was used as a support, and a 5% by weight methanol solution of a polyamide resin (trade name: Amilan CM8000, manufactured by Toray Industries, Inc.) was applied to the support by a dipping method to give 0. An undercoat layer having a thickness of 0.5 μm was provided.

Then, the following structural formula (II)

[0042]

[Chemical 1] 2 parts of bisazo pigment (1 part by weight of resin A of the following structural formula (III))

[0043]

[Chemical 2] And 100 parts of cyclohexanone were dispersed for 20 hours in a sand mill using glass beads having a diameter of 1 mm. Tetrahydrofuran (100 parts) was added to this dispersion, and the solution was coated on the undercoat layer.

Next, 9 parts of compound B of the following structural formula (IV)

[0045]

[Chemical 3] And bisphenol Z type polycarbonate (trade name: Z
10 parts of -200, manufactured by Mitsubishi Gas Chemical Co., Inc.) was dissolved in 100 parts of monochlorobenzene. This solution was applied onto the charge generation layer and dried with hot air at 100 ° C. for 1 hour to give a thickness of 2
Charge transport layers of 0, 25 and 28 μm were formed.

Example 2 Instead of the charge transport material B in Example 1, a compound C represented by the following structural formula (V)

[0047]

[Chemical 4] The same procedure as in Example 1 was carried out except that was used to form charge transport layers having thicknesses of 20 and 25 μm, respectively.

Example 3 Instead of the charge transport material B in Example 1, a compound D represented by the following structural formula (VI)

[0049]

[Chemical 5] Was used, and the same procedure as in Example 1 was performed except that the polymethylmethacrylate resin (E) was used instead of the bisphenol Z type polycarbonate.

Comparative Example 1 In Example 1, the charge transporting layer was prepared in exactly the same manner except that the film thicknesses were 30 and 35 μm, respectively, and the same coating was applied.

Comparative Example 2 The procedure of Example 2 was repeated, except that the film thicknesses of the charge transport layer were 28 and 30 μm, respectively.

Comparative Example 3 The procedure of Example 3 was repeated, except that the thicknesses of the charge transport layers were 32 and 35 μm, respectively.

The photoconductor thus prepared was evaluated as follows. A conductive filler (carbon less than 10 ² Ω · cm, titanium oxide, etc.) is dispersed in an insulating resin to a length of 350.
mm, 10 mm wide, applied on a curved stainless steel plate,
After drying, the charging member was molded. Volume resistance is 10 ⁷
It was Ω · cm. The distance (gap) between the photoconductor and the charging member was 70 μm.

A sample for capacitance measurement was prepared by winding an aluminum sheet on an aluminum cylinder and then applying a photosensitive layer under the same conditions. The capacitance was measured with an impedance measuring device (YHP 4192A).

As a basic form, the electrophotographic apparatus is based on Canon NP3525, and has an image exposure means, a developing device,
The paper feeding system, the transfer charging device, the conveying system and the pre-exposure means are used as they are, and the above-mentioned curved plate-like charging member and cleaner are used as the primary charging means for cleaning only by blade cleaning with a blade made of silicon rubber. Remodeled into. The voltage applied to the charging unit is DC-23.
Only 00V (no superposition of AC voltage) was set. In addition, copying was performed in an environment of a temperature of 23 ° C. and a humidity of 50%.

Comparative Example 4 The procedure of Example 1 was repeated except that the distance (gap) between the photosensitive member and the charging member was set to 400 μm. As for the image, halftone and solid black images were copied by the above-mentioned image forming apparatus, and the uniformity of charging and the like were evaluated from image defects such as stripes. The results are shown in Table 1.

[0057]

[Table 1] Table 1

[0058]

As described above, according to the present invention, charging is uniform, and a good image having no image defects such as stripes can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a basic configuration of an electrophotographic apparatus of the present invention.

FIG. 2 is a schematic diagram showing a basic configuration of an electrophotographic photosensitive member of the present invention.

FIG. 3 is a schematic diagram showing a basic configuration of an electrophotographic photosensitive member of the present invention.

FIG. 4 is a schematic diagram showing a basic configuration of an electrophotographic photosensitive member of the present invention.

FIG. 5 is a schematic view showing a specific example of the electrophotographic apparatus of the present invention.

FIG. 6 is a block diagram showing a configuration of a facsimile using the electrophotographic apparatus of the present invention as a printer.

Continuation of the front page (56) Reference JP-A 63-149669 (JP, A) JP-A 6-36858 (JP, A) JP-A 5-223513 (JP, A) JP-A 5-210283 (JP , A) JP-A-5-150539 (JP, A) JP-A-5-107866 (JP, A) JP-A-5-34964 (JP, A) JP-A-5-27468 (JP, A) JP-A-5-27468 (JP, A) 2-67575 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 5/00

Claims (2)

(57) [Claims] 1. An electrophotographic photosensitive member and a charging member disposed in proximity to the electrophotographic photosensitive member in a non-contact manner .
The volume resistance value is in the range of 10 ⁰ to 10 ¹² Ω · cm, and the distance (gap) l between the electrophotographic photosensitive member and the charging member satisfies the following relational expression (I), and is 30 μm. ≦ l ≦ 90 μm (I) An electrophotographic photoreceptor for an electrophotographic apparatus, wherein the surface of the electrophotographic photoreceptor is charged by applying only a DC voltage to the electrophotographic photoreceptor from the charging member. The electrostatic capacitance C per 1 cm ^{2 of the} photoconductor is 95 pF or more and 140 pF
An electrophotographic photoreceptor characterized by the following: 2. An electrophotographic photosensitive member and a charging member disposed in proximity to the electrophotographic photosensitive member in a non-contact manner .
The volume resistance value is in the range of 10 ⁰ to 10 ¹² Ω · cm, and the distance (gap) l between the electrophotographic photosensitive member and the charging member satisfies the following relational expression (I), and is 30 μm. ≦ l ≦ 90 μm (I) In an electrophotographic apparatus for charging the surface of the electrophotographic photosensitive member by applying only a DC voltage from the charging member to the electrophotographic photosensitive member, 1 cm ^{2 of the} electrophotographic photosensitive member The electrostatic capacity C is 95 pF or more and 140 pF or less .